Piston turning lathe

ABSTRACT

A piston-turning lathe comprising a head carrying the work spindle and a tool head provided with cutting tools for preliminary and finish machining of pistons during rotation of the spindle. The lathe also has a drive for synchronous rotation of the tool head spindle and work head spindle and devices for displacing the work head spindle axis in two mutually perpendicular planes relative to the axis of the tool head spindle, said spindles being installed with a provision for turning their axes in the direction of working feed while the work head spindle is, additionally, installed with a provision for inclining its axis in the same direction, and there is also a means for mutual relative turning of the work head and tool head spindles by the mechanism for setting the tool holders with the cutting tools for preliminary and finish machining.

United States Patent 1 Fedorenko et al.

[ 51 May 15, 1973 PISTON TURNING LATHE 22 Filed: Oct.5, 1971 21Appl.No.: 186,721

52 U.S.Cl ..s2/19 [51 met. .1123!) 5/24 [58] FieldofSearch ..s2 19,1s,2o

[5 6] References Cited UNITED STATES PATENTS 3,391,587 Van Den Kieboom..82/19 2,720,806 10/1955 Stewart ..82/l8X Primary Examiner-LeonidasVlachos [57} ABSTRACT A piston-turning lathe comprising a head carryingthe work spindle and a tool head provided with cutting tools forpreliminary and finish machining of pistons during rotation of thespindle.

The lathe also has a drive for synchronous rotation of the tool headspindle and work head spindle and devices for displacing the work headspindle axis in two mutually perpendicular planes relative to the axisof the tool head spindle, said spindles being installed with a provisionfor turning their axes in the direction of working feed while the workhead spindle is, additionally, installed with a provision for incliningits axis in the same direction, and there is also a means for mutualrelative turning of the work head and tool head spindles by themechanism for setting the tool holders with the cutting tools forpreliminary and finish machining.

7 Claims, 16 Drawing Figures PAIENTL MAY 1 51373 SHEET 1 [IF 7 7PATENTED HAY] 5M3 sum 5 or 7 PISTON TURNING LATHE The present inventionrelates to the machine-tool building industry and more specifically itrelates to lathes for machining the pistons of internal-combustionengines.

Serviceability, reliability and longevity of internalcombustion enginescalls for an improvement in the reliability and serviceability of theirmost vital parts, which include their pistons.

Engine pistons are subjected to the action of both mechanical andthermal loads. Owing to irregular distribution of metal around thecircumference of the piston caused by the necessity of providing bossesfor the piston pin, the external surface of the piston expandsnonuniformly, the greatest expansion taking place along the piston pinaxis. ln order to make the crosssectional profile of the piston in theoperating condition conform as nearly as possible to a circumference,the cold piston has an oval shape with a smaller axis directed along thepiston pin axis. The longitudinal profile of the piston skirt is mostoften made in a tapered or barrel shape.

Up to the present time the pistons have been machined by grinding orform-tuming. However, the form-turning process has a number of inherentdisadvantages.

Firstly, this method has low efficiency due to a rigid contact betweenthe feeler rod and the master form, i.e. to the allowable accelerationof the working elements of the machine tools which have a definite mass,so that high machining speeds create considerable forces of inertiawhich causes the feeler rod to jump away from the master form.

Secondly, the accuracy of the machined surface of the work depends onthe surface finish of the master form, its wear, and on the inaccuraciesof the machine components which transmit motion from the master form tothe cutting tool.

Thirdly, too much labor is required for designing and making masterforms, especially the three-dimensional ones and those having a variablecross-sectional profile along the length of the piston.

While form-grinding pistons, the abovelisted disadvantages areaggravated by those inherent in grinding, i.e. by heavy cutting forceswhich distort the piston skirt and impair the accuracy of itscross-sectional shape, and by embedding the abrasive particles into thesurface of the piston skirt which is highly objectionable during theoperation of the engine.

Besides form-turning lathes there are lathes for turning the pistonalong an ellipse. Considerably wide application has been found forlathes which turn the pistons with elliptical skirts, said lathesutilize an inclined plane which produces an ellipse in the cylindercutting operation.

This principle is employed in the lathes described in the followingpatents:

No. 665,486, Cl.49a, Group II, 1938, Germany.

No. 2,121,934, Cl.82l5, 1938, USA.

No. 2,924,135, Cl.8219, 1960, USA.

No. 1,483,369, Cl.B23b, 1966, France.

No. 1,516,951, Cl.823b, 1967, France.

The prototype most closely resembling the lathe claimed herein is thepiston-turning lathe described in U.S. Pat. No. 2,720,806, 1955.

This lathe incorporates a bed with a table which is movable in alongitudinal direction. A work head with a clamping device for fixingthe piston is rigidly fastened to the table. A bridge is mounted on thetop of the bed which supports the tool head which is set so that thelongitudinal axis of its spindle lies in the vertical plane and passesthrough the longitudinal axis of the piston being machined with a meansfor inclination through a small angle (O.5 4) to the piston axis. Thepath of the cutting tool clamped in the tool holder of the tool headspindle, although it is circular with respect to the axis of the spindleof this head, forms an ellipse, which is projected onto the crosssection of the piston. The longitudinal profile of the piston is formedsimultaneously with the elliptical cross section by means of alongitudinal master form which moves in the hollow spindle of the toolhead in synchrony with the lathe table which carries the work head andthe piston.

This lathe is capable of producing only the elliptical cross section.However, the elliptical cross section of the piston can prove optimumonly in an individual case since cross-sectional profiles of the pistonsvary with engine operation temperatures, with compression ratio, enginepower, mass of the pistons and their design features. These factorsgovern the optimum cross and longitudinal shapes of the piston skirt. Asa consequence, each engine must have pistons with definite cross andlongitudinal sections, the cross sections of the piston always differingin elliptical shape.

An object of the present invention resides in providing a piston-turninglathe which would produce a range of highly accurate piston profilecross sections, namely elliptical, enveloping an ellipse, enveloped byan ellipse, either constant or variable throughout the length of thepiston, and simultaneously producing a tapered or barrel-shaped profilein the longitudinal section of the piston.

This and other objects are achieved by providing a piston-turning lathecomprising a movable table mounted on the lathe bed with a head carryingthe work spindle, a tool head installed on a bridge mounted on the lathebed, said head being fitted with cutting tools for preliminary andfinish-machining of pistons during rotation of the spindle whichaccommodates inside a longitudinal master form contacting the mechanismfor setting the tool holders with cutting tools for preliminary andfinish machining, and a drive for synchronous motion of the longitudinalmaster form and the table with the work head. According to theinvention, the lathe incorporates a drive for synchronous unidirectionalrotation of the tool head spindle and work head spindle, the angularspeed of the tool spindle being twice as high as the angular speed ofthe work spindle, and has means for displacing in two mutuallyperpendicular planes the axis of the work head spindle relative to theaxis of the tool head spindle, these spindles being installed with ameans for turning their axes in the direction of working feed while thespindle of the work head is also equipped with a provision for incliningits axis in the same direction, and it also has a means for relativeturning of the work head spindle and tool head spindle by the mechanismfor setting the tool holders with the cutting tools for preliminary andfinish machining of pistons.

Such a design makes it possible to provide a lathe for machining pistonswhose cross profiles can be ellipti- 33 cal, enveloping an ellipse andenveloped by an ellipse, either constant or variable along the length ofthe workpiece, while their longitudinal profiles can be either taperedor barrel-shaped.

It is practicable that said drive for synchronous unidirectionalrotation of the tool head spindle and work head spindle should be madein the form of a gear-anduniversaI-joint drive with a gear transmissionto the tool head shaft having a speed ratio of 1:2 and a geartransmission to the work head spindle having a speed ratio of I21, bothgear transmissions being interconnected by a universal joint drive. Thismakes it possible to connect kinematically the piston and the tool,ensuring such a relative motion which would produce the presetcross-sectional profile of the piston.

It is also practicable that the axes of the work head and tool headspindles should be relatively displaced in two mutually perpendicularplanes by means of screwand-nut pairs acting in the above-stated planeson the body of the work head.

This enables the setting of the relative positions of the axes of thework and tool head spindles for machining various cross-sectionalprofiles, namely elliptical, enveloping an ellipse and enveloped by anellipse- It is also practicable to turn the axis of the tool headspindle relative to the direction of working feed on-the bridge whichhas a pin on which the tool head is placed in such a manner that the pinaxis would pass through the point where the axis of the tool headspindle intersects the plane passing through the tops of the tool headcutters perpendicularly to the spindle axis.

This turning of the tool head spindle axis relative to the direction ofworking feed ensures the possibility of changing the curvature of thecross profiles enveloping an ellipse or enveloped by an ellipse, i.e. itpermits obtaining a range of oval curves at constant values of thelarger and smaller axes of the cross profile. Installation of the toolhead on the pin so that the axis of said pin passes through the point ofintersection of the tool head spindle axis with the plane passingthrough the tops of the tool head cutters, square to the spindle axis,makes it possible to change the curvature of the profile, i.e. to obtaina range of oval profiles with constant values of the larger and smalleraxes of the cross profile without additional setting of the relativepositions of the work head and tool head spindle axes.

It is also expedient that, for inclining the axis of the work headspindle in the direction of the working feed in the plane perpendicularto the plane of turning the tool head spindle, the lathe should beprovided with a device in the form of a sine table with inclined plates.This makes it possible to produce cross sections of pistons enveloped byan ellipse and varying along the machining length.

It is no less practicable that for turning the axis of the work headspindle in the direction of the working feed in the plane coincidingwith and parallel to the plane of turning of the tool head spindle, thelathe should be provided with a swivelling carriage with a hole fittingover the pin secured to the upper plate of the sine table. This ensureselliptical and enveloping an ellipse cross sections of the pistons,variable along their machining length.

It is also expedient that the means for relative turning of the workhead spindle and tool head spindle during operation of the mechanism,for setting the holders with the cutting tools, and for preliminary andfinish machining should be made in the form of a vane cylinder whosebody should carry the gear of the work head gear drive and the bodyproper should be installed with a provision for turning on the driveshaft, the latter being rigidly connected to the vanes.

The relative turning of the work head spindle and tool head spindleduring operation of the mechanism for setting the tool holders withtools for preliminary and finish machining makes it possible to carryout preliminary and finish machining of the workpiece at one setting-upwhich excludes the errors of basing and clamping which occur if theworkpiece is machined on two lathes, and thus ensuring completemachining of the piston skirt on one machine instead of two.

As a result of the present invention, we provide a lathe for machiningpistons which ensures a highly accurate range of profiles of pistoncross sections: elliptical, enveloping an ellipse, enveloped by anellipse, either constant or variable throughout the length of theworkpiece with simultaneous provision of a tapered or barrel-shapedprofile in the longitudinal section of the skirt.

Now the invention will be described in detail by way of example withreference to the accompanying drawings, in which:

FIG. 1 is a side view of the piston-turning lathe according to theinvention, partly cut away longitudinally;

FIG. 2 same, top view, cut out longitudinally;

FIG. 3 is fragment A in FIG. 2;

FIG. 4 is a section taken along line IV-IV in FIG. 3;

FIG. 5 is a section taken along line VV in FIG. 2;

FIG. 6 is fragment B in FIG. 2;

FIG. 7 shows the paths of the cutting tools and the arrangement of thecross-sectional profiles of the piston skirt relative to the axes of thework head and tool head spindles after machining of the piston skirt,with the cutting tools set for preliminary and finish machining;

FIGS. 8 through 12 illustrate the arrangements of the spindle axes ofthe work head and tool head at different settings of the machine and thepaths of the cutting tools in the plane perpendicular to the work axis;

FIGS. 13 14 show the cross-sectional profiles of the piston skirts afterthey have been machined at different settings of the lathe;

FIGS. 15 16 show the nature of the changes in the profile of the pistonskirts with the cross sections varying along the piston length atdifferent settings of the lathe.

The claimed lathe illustrated in FIGS. 1 through 6 has a bed 1 (FIGS. 12) of the corresponding size, appropriately secured, and provided withguide surfaces 2 over which the table 3 moves progressively in thedirection of 0, 0,.

The lathe is provided with some means (hydraulic drive) for the uniformfeed of the table 3 over the guide surfaces 2 of the bed I though thesemeans are not part of the present invention and are not, therefore,shown in the drawings.

The work head 4 is mounted on the lathe table 2 and consists of a body 5carrying the work spindle 6 installed on bearings, said spindlecarryinga chuck 7 for clamping the piston (workpiece) 8.

When the piston 8 is clamped in the chuck 7, the piston axis gets inline with the axis of the spindle 6 so that axis 0 0, will hereinafterbe referred to as the piston rotation axis.

Mounted and fastened on the spindle 6 of the work head 4 is a gear 9which meshes with the gear 10 rigidly secured on the body 11 of the vanecylinder 12. The speed ratio of the gears 10 and 9 is lzl. The body 11of the vane cylinder 12 is rotatably mounted on a drive shaft 13. Thevanes 14 (FIG. 4) rigidly secured on the drive shaft 13 at diametricallyopposite sides are aligned by the inner cylindrical surface 15 of thebody 11 of the vane cylinder 12 and are tightly closed by cover 16 (FIG.3). Segment stops 17 (FIG. 4) mounted and fastened on the innercylindrical surface 15 of the vane cylinder body 11 form, together withthe vanes 14, working spaces 18 and 19.

The working fluid (compressed air or liquid) is fed into the relevantworking spaces through channels 20 and 21 in the drive shaft 13 with theaid of a distributor 22 (FIG. 3) slipped on the end of the drive shaft12 and fastened to the body 5 of the work head 4.

The distributor 22 has two inlet channels 23 and 24 which supply theworking fluid to the relevant spaces 18 or 19 of the vane cylinder 12during rotation of the drive shaft 13.

When the working fluid is fed through the channel 24 of the distributor22 and channel 21 of drive shaft 13 to the space 18 of the vane cylinder12, the vanes 14 together with the drive shaft 13 will turn relativelyto the body II of the vane cylinder 12 through an angle limited by thesegment stops 17. In the present version of the lathe this angle ofturning of the drive shaft 12 with the vanes 14 relative to the body IIof the vane cylinder 12 with the gear 10 is equal to 90.

When the working fluid is fed into the space 19 through the channels 23and 20, the drive shaft 12 with the vanes 14 returns to the initialposition relative to the segment stops 17 as shown in FIG. 4.

The body 5 of the work head 4 is installed on carefully fitted dovetailsurfaces 25 (FIG. 1) which allows the body 5 and, consequently, thepiston rotation axis 0 0 to be displaced during adjustment in ahorizontal plane by means of a screw-and-air pair whose screw 26 (FIG.2) is installed in the body 5 while a nut 27 (FIG. 1) is fastened in thecarriage 28.

The carriage 28 is secured on the plate 29 whose lower surface 30 isinclined and installed on an inclined surface of a plate 31 which allowsa screw-and-nut pair whose screw 32 is set in the plate 29 parallel tothe inclined surface 30 and the nut 33 is secured on the inclinedsurface of the plate 31 to move the piston axis 0 0 in a vertical planeparallel to itself. Besides, the

carriage 28 can turn around the pin 34 secured on the plate 29, thuschanging the angular position of the piston axis 0 0 in a horizontalplane relative to the direction the table feed 0 0 through angle A (FIG.2).

A plate 31 is articulated by a pivot 35 (FIG. 1) to a plate 36 securedon the lathe table 3 and is pressed by a cylindrical support 37 againstthe ground shoulder 38 of the plate 36 thus forming a kind of a sinetable which makes it possible to change the angular position of theplate 31 and, consequently, of the piston axis 0, 0, in a vertical planerelative to the direction of the table feed 0 0 with the aid of a set ofgauge blocks (not shown in the drawings).

The tool head 39 consists of a body 40 in which a hollow spindle 41 isinstalled on bearings, with the axis of rotation 0 0 said spindlecarrying the tool holders 42 and 43 with cutting tools 44 and 45.

Tool holders 42 and 43 are installed in spindle 41 on ball supports 46and interconnected by sliders 47 and 48 and by spring 49 with thelongitudinal profile master form 50.

The master form 50 (FIG. 5) has two forming surfaces 51 and 52 whichcome in contact with the sliders 47 and 48 in the working position.

The master form 50 with the forming surfaces 51 and 52, the sliders 47and 48, and the spring 49 constitute a mechanism for setting the toolholders 42 and 43.

The master form 50 is oriented relative to the spindle 41 and sliders 47and 48 by means of a keyway 53 which receives a key 54 secured to thespindle 41 which allows only an axial movement of the master form 50 inthe spindle 41.

The body of the tool head 39 is secured rigidly to plate 55 (FIGS. 1, 2)which, in turn, is located on a bridge 56 with a provision for changingthe position of the spindle rotation axis 0 0 through angle ill byturning around a pin 57 installed on the bridge 56.

The progressive motion of the lathe table 3 and that of the longitudinalprofile master form 50 are synchronized by means of a rack-and-geardevice 58 consisting of a body 59 secured on the bed 1, said bodyaccommodating a shaft installed on rolling-contact bearings and carryinga rigidly secured gear 61, and electromagnetic coupling 62 with a gear63. The gear 63 meshes with the gear rack 64 fastened to the table 3,whose motion is imparted to the gear 63; upon energizing electromagneticcoupling 62 rotation is transmitted to the shaft 60 and gear 61.

The gear 61 is connected by an idler gear 65 with a gear rack 66 securedon a carriage 67 which moves over guide bars 68. The guide bars 68 arelocated on a body 69 rigidly connected with the swivelling plate 55. Theidler gear 65 has a sliding fit on the axle 70 which is secured rigidlyin the plate 71. The plate 71 is installed on the body 69, ensuringconstant mesh of the idler gear 65 with the rack 66.

The idler gear 65connects the gear 61 with the gear rack 66 when theposition of the axis 0, 0 of the tool head spindle 41 is changed througha corresponding angle ill.

The carriage 67 has a cylinder 72 which ensures the movement of thepiston 73; installed on a bearing 74 in said cylinder 72 is a rod 75articulated to the longitudinal profile master form 50.

The cylinder 72 has two working spaces 76 and 77 (FIG. 6). The space 76is formed by the piston 73 and the rear cover 78 while the space 77 isformed by the piston 73 and the front cover 79. The piston stroke isadjusted by a nut 80 and fixed by a lock nut 81.

The preliminary machining of the piston (workpiece) 8 is started withthe piston 73 in the forward position when the pressure of the workingfluid (compressed air or liquid) fed into the space 76 brings it incontact with the thrust surface 82 of the nut 80.

Rotation of the tool head spindle 41 is transmitted from the electricmotor via a V-belt drive (not shown in the drawings) and pulley 83(FIGS. 1, 2). The spindle 41 carries a gear 84 (FIGS. 1, 2) which is inmesh with the gear 85 mounted on the shaft 86. The speed ratio of thegears is 1:2. Accordingly, the spindle 6 of the work head 4 is rotatedby gears 88 and 89, splined shaft 90 and splined bushing 91, drive shaft13 and gears 10 and 9 in the same direction as the'spindle 41 of thetool head 39 but at half the angular speed because the speed ratio ofthe gears 84 and 85 is 1:2.

In order to obtain the required shape of the piston skirt, the piston(workpiece) 8 is clamped in the chuck 7. Upon starting the lathe, thetable 3 together with the work head 4 is fed rapidly by the hydraulicsystem towards the cutting tools of the spindle of the tool head 39after which the table 3 is moved at a working feed along axis 0'.

Concurrently with starting the working feed of the table 3 from theelectric motor, rotation is transmitted via the V-belt drive and pulley83 to the spindle 41 of the tool head 39, while the spindle 6 of thework head 4 is rotated via gears 84 and 85, shaft 86, universal jointdrive 87, drive shaft 13 and gears and 9.

But, since the speed ratio of the gears 84 and 85.is equal to l:2, thetoo] head spindle 41 rotates at an angular speed 2wt in synchronism withthe spindle 6 of the work head 4 whose angular speed is wt.

Synchronization of the progressive movement of the table 3 with that ofthe longitudinal profilemaster form 50 is ensured by the rack-and-geardevice 58 whose electromagnetic coupling 62 is energized simultaneouslywith turning on the working feed of the table 3. When theelectromagnetic coupling 62 is energized, the progressive motion of thetable 3 is transmitted by the rack 64, gear 63, shaft 60, gears 61 and65 to the rack 66 which is rigidly connected to the carriage 67 so thatthe latter moves at a speed which is equal to the speed of the workingfeed of the table 3, but in the opposite direction. The piston 73 is inthe forward position (as shown in FIG. 2) in the cylinder of the movingcarriage 67 and imparts progressive motion via the rod 75 to thelongitudinal profile master form 50 which rotates together with thespindle 41.

The master form 50 has two forming surfaces 51 and 52 in the form offlats; in the position shown in FIGS. 2 and 5 the surface 51 is incontact with the slider 47 which corresponds to the working position ofthe tool holder 42. At this moment the second slider 48 comes in contactwith the rectilinear generatrix of the cylindrical surface of thelongitudinal profile master form 50 which corresponds to the nonworkingposition of the tool holder 43. During axial motion of the master form50 the cutting tool 44 of the tool holder 42 occupying the workingposition, moves in accordance with the law set by the forming surface 51while the cutting tool 45 stays withdrawn from the machined surfacebecause the slider 48 installed in the tool holder 43 is in contact withthe rectilinear generatrix of the cylindrical surface of the master form50.

The use of the master form 50 allows obtaining actually any profile(tapered, barrel-shaped, etc.) in the longitudinal section of the piston8 because copying is carried out at low speeds which are equal to thespeed of the table working feed, the manufacture of the longitudinalprofile master forms being quite simple.

At the end of the travel of the table 3 towards the tool head 39, Le.after preliminary turning of the piston with the cutting tool 44installed on the tool holder 42, the tool holders 42 and 43 changeautomatically their positions because the piston 73 in the cylinder ofthe carriage 67 moves to the rearmost position when the service fluid isfed into the working space 77. Inasmuch as the stroke of the piston 73is somewhat longer than the length of the workpiece surface beingmachined, the tool holder 42 is withdrawn, together with the cuttingtool 44, from the surface being machined during the longitudinalmovement of the master form 50 and occupies a nonworking position whilethe tool holder 43 carrying a diamond cutting tool 45 for the finalmachining occupies the working position with the aid of the slider 48due to transition from the rectilinear generatrix of the cylindricalsurface of the master form 50 to the forming surface 52 and due to theforce of the spring 49. When the table 3 moves in the opposite direction(from the tool head 39) at the working feed, the carriage 67 with thepiston 73 in the rearmost position moves the longitudinal profile masterform 50 which, in its turn, moves the slider 48 and, as a consequence,the tool holder 43 with the cutting tool 45, along the profile set bythe forming surface 52.

When the piston (workpiece) 8 is machined in two passes, i.e., bypreliminary and finish machining, it must be taken into account thatprofile C (FIG. 7) formed by the cutting tool 44 during preliminarymachining proves to be symmetrical with the central point 0 (0 is thecentral point of cross sections of the pistons in the normal section ofaxis 0 0 so that the finish machining cutting tool 45 should have aradius of rotation with relation to point 0 where the rotation axis (l-0 of the spindle 41 of the tool head 39 intersects the plane passingthrough the top of the cutting tools 44 and 45, perpendicularly to theaxis 0 0 said radius being 21 1 larger than the radius of rotation ofthe cutting tool 44 which is equal to 1 where 1 is the value of therequired clearance. However, account should also be taken of the cuttingdepth t of the cutting tool 45 for final machining. Thus, the radius ofrotation of the cutting tool 45 around the point 0 should be larger thanthe radius of rotation of the cutting tool 44 by the value of R 21 t 1so as not to touch upon the surface being machined.

Upon shifting the tool holders 42 and 43 with the cutting tools 44 and45 after preliminary machining, i.e., when the tool holder 42 with thecutting tool 44 is withdrawn from the machined surface and the toolholder 43 with the cutting tool 45 is contacted with this surface, thecutting tool 45 will occupy a position diametrically opposite to thecutting tool 44 and will cut the workpiece along the profile D" (FIG. 7)turned through relative to the profile C which has been machined by thecutting tool 44. Therefore, during successive machining with two cuttingtools, apart from shifting the tools, i.e. feeding the service fluidinto the space 77 of the cylinder 72 of the carriage 67, it is necessaryto turn the workpiece 8 through 90 with relation to thefinal-machiningcutting tool 45, Le. to turn the spindle 6 of the work head 4 withpiston 8 relative to the spindle 41 of the tool head 39.

Relative turning of the spindle 6 of the work head 4 and spindle 41 ofthe tool head 39 will take place when the working fluid is deliveredinto the spaces 18 of the vane cylinder 12 through channels 24 and 21.This will turn the drive shaft 13 with the vanes 14 relative to thesegment stops 17 of the vane cylinder 12. Since the gear 10 is securedon the body 11 of the vane cylinder and meshes with the gear 9 securedon the spindle 6 of the work head 4, and the drive shaft 13 is connectedby a gear-and-universal-joint drive with the spindle 4l of the tool head39, this ensures the required relative turning of the spindles 6 and 41.The body 11 of the vane cylinder 12 is fixed on the drive shaft 13 aftereach revolution by the elements which are not part of the presentinvention and are not shown in the drawings.

The service fluid is fed simultaneously into the space 18 of the vanecylinder 12 and into the space 77 of the cylinder 72.

After final turning of the skirt of the piston 8 by the cutting tool 45,rotation of the spindles 41 and 6 is stopped, they are braked, the toolholders 42 and 43 exchange places while the piston 73 moves in thecylinder 72 of the carriage 67 to the initial foremost position, thespindles 41 and 6 turn relative to each other to their initialpositions, the electromagnetic coupling 62 is deenergized, the carriage67 is stopped and the table 3 is rapidly moved to the initial position.The machined piston 8 is withdrawn and the working cycle is repeatedover again.

Different profiles of the piston skirt, both constant and varying inlength, can be obtained by appropriate settings of the lathe.

The piston profiles which are constant in length can be produced whenthe workpiece rotation axis 0 is turned relative to the direction 0, 0,of the table feed through an angle of 0 ()t 0) both in the horizontaland vertical planes.

When the piston 8 is rotated around the axis 0 0 such as (in the case ofmachining profiles that are of constant length and coinciding with theaxis of table feed 0, 0,) at an angular speed of wt while the cuttingtools 44 and 45 whose working radius of rotation is 1, rotate at anangular speed of 2wt around the axis 0 0 which in this case coincideswith the axis 0 0,, and the point 0 of intersection of the axis 0,, 0coincides with the plane passing through the tops of the cutting toolsperpendicularly to the axis 0,, 0 belongs to the axis 0 0 (as shown inFIG. 8) in the cross section of the piston 8, i.e. in the planeperpendicular to the axis 0 0,, this produces a circumference with aradius 1, (curve 6 in FIG. 13).

This is obtained by setting the plate 55 with the tool head 39 (and,consequently, the axis 0 0 parallel to the direction of table feed 0, 0,with subsequent correction of the position of the piston axis 0 0 in thevertical plane by the screw-and-nut pair 32, 33, and in the horizontalplane by the screw-and-nut pair 26 and 27.

By setting the axis 0 0 of the piston 8 parallel to the rotation axis 00 of the spindle 4I of the tool head 39 (FIG. 9) and, correspondingly,parallel to the direction 0, 0, of the feed of the table 3, butdisplacing it by a value of 1 by the screw-and-nut pair 26, 27, weobtain a cross section of the skirt of the piston 8 in the shape of anellipse with a smaller semiaxis equal to 1, 1 and a large one, equal to1, 1 (curve F in FIG. 13).

To obtain a curve enveloping an ellipse with semiaxes 1, 1 and l, 1 andpassing through the points of its larger GG and smaller HH axes (curveI, FIG. 13), i.e. a curve changing the curvature of the profile in eachquarter it is necessary, apart from parallel displacement of the pistonrotation axis 0 0 and rotation axis 0 0 of the tool head spindle 41through angle 4; in the horizontal'plane so that the axis of turningaround the pin 57 would pass through the point 0 of intersection of theaxis 0 0;, and the plane passing through the tops of the cutting tools44, 45, perpendicular to the axis 0,, 0 and would. be located at adistance of 1 from the rotation axis 0 0 of the piston 8. When thespindle 41 of the tool head 39 is turned through angle 41 the path ofthe cutting tool in the plane perpendicular to the rotation axis 0 0 ofthe piston 8 will be described by ellipse M (FIG. 10).

Thus, the ellipse (curve F in FIG. 13) obtained by parallel displacementof the rotation axis 0 0 of the piston 8 and the rotation axis 0 0 ofthe spindle 41 of the tool head 39 is corrected in each quarter by themovement of the cutting tools along the ellipse M. Depending on theangle of turning ll! of the spindle of the tool head 39 said ellipsemakes it possible to produce different curvatures of the cross sectionof the skirt of the piston 8; in this case the rotation radius of thecutting tool relative to the axis 0 0 should be 1,/cosr11.

The oval curves enveloped by the ellipse (curve N, FIG. 13) can beobtained if the projection of the cutting tool path (in the planeperpendicular to the axis 0 0 is described by ellipse P shown in FIG.11, Y

which is achieved by turning the spindle 41 of the tool head 39 throughangle ill in a horizontal plane. However, the radius of rotation of thecutting tools around the axis 0 0 should in this case be 1, and therotation axis 0 0 of the piston is moved in the vertical plane (i.e. inthe plane perpendicular to the turning plane of the tool head spindle)by the screw-and-nut pair 32, 33 for a value of 1 relative to the point0 where the rotation axis 0 --0 of the spindle 41 of the tool head 39intersects the plane passing through the tops of the cutting tools 44and 45, perpendicularly to the axis 0 0 When the rotation axis 0 0 ofthe piston 8 is displaced through 1 relative to the point 0 at a certainacute angle to the turning plane of the tool head spindle (FIG. 12),asymmetrical curves can also be obtained. FIG. 14 shows an example ofasymmetrical curve Q enveloping the ellipse F.

As a matter of fact, asymmetrical curves are not used in the pistonmachining practice; however, as much as the pistons are worn moreheavily on one side than on the other, such curves probably will becomeof use in the future.

As a rule, the rotation turning angle 1!; of the tool head spindleduring machining of pistons from different engine may vary from 0 to330. T

The rotation radius 1, of the cutting tools and the displacement 1 ofthe axes of the tool head and work head spindles are selected to suitthe diameter of the piston. For example, for the piston of 76 mmdiameter and a decrease in the profile curve equalling 0.206 mm, 1=0.0515 mm and 1,=37.9485-mm. Y

The claimed lathe can be used for machining the surfaces of the pistonswith the cross sections varying along the length of said pistons. Thevariable cross sections are characterized in that the larger GG andsmaller HH axes (FIG. 15) of the oval curves change through out thelength L of the piston surface being machined.

The pistons with a variable cross profile are machined on the claimedlathe at a certain angle in the vertical or horizontal planes of therotation axis 0 0 of the piston 8 relative to the direction 0, 0, of thetable feed.

When the table 3 with the work head moves in the direction 0, 0, of itsfeed, with the workpiece rotation axis 0,0 turned through the value ofaxis displacement 1 relative to the point 0 changes along the length ofthe work. This value 1 can increase or decrease by acorrespondin'g'increment L.tg A A (where L= length of piston machining)depending on the side in which the piston rotation axis 0 is turnedthrough angle A.

Angle A is formed by the piston rotation axis 0, 0 and the direction 0 0of table feed passing through the point 0 where axis 0 0 is crossed by aplane perpendicular to it.

Displacement 1 of axes is increased when, during displacement of theworkpiece relative to the point 0 the side of angle A formed by thedirection 0 0 of table feed is located nearer to said point. In case ofthe contrary arrangement of the sides of angle A, i.e. when axis 0 0 islocated nearer to the point 0 displacement of axes 1 is decreased.

In the setup shown in FIG. 2, when the table moves towards the toolhead, the displacement 1 of axes is increased and the larger semiaxis onthe length of machining L at a constant rotation radius 1, of thecutting tools increases by the value Ltgk whereas the smaller semiaxisdecreases by the same value as shown in FIG. 15. Hence, when alongitudinal profile is machined in the plane passing through the largeraxes GG and G G of the cross sections, the master form 50 beingdisengaged, the generatrix R will be rectilinear and tapered with thelarger base G G Inasmuch as the maximum cross section diameter of thepiston skirt near the piston head (section G,G I-I I-I in FIG. must besmaller than near the skirt face end (i.e. G6 G G an equidistant profilewith shorter large and small axes G G and H H can be obtained by takingin account the value of A while profiling the forming surfaces on thelongitudinal profile master form 50.

By changing the tool rotation radius 1 on the machining length L withthe aid of the master form moving in synchronism with the piston 8, itis possible to obtain a tapered longitudinal profile (generatrix S, FIG.15) or a barrel-shaped profile (generatrix T, FIG. 15). Such shapes aremost characteristic of the pistons with a variable profile.

If the axis displacement 1 on the length of machining L is decreased byLtg A,-the larger semiaxis of the cross section is decreased and thesmaller semiaxis is increased (FIG. 16).

The curves of the piston cross sections which are variable in length,i.e. elliptical, enveloping an ellipse and enveloped by an ellipse, canbe obtained by using the machine setups similar to those used forobtaining the constant sections along the length of the workpiece shownin FIGS. 8-12, with the sole difference being that the axis 0 0 isturned or inclined to a required angle A.

The elliptical curve which varies along the piston length can beobtained when the spindle 41 of the tool head 39 is turned through angle1!: 0 and the piston rotation axis 0 0 is displaced through the requiredangle A in the horizontal plane (i.e. turning plane of the tool headspindle) to a value of I, relative to point 0 (curve F FIG. 15).

The curves that vary along the piston length and envelop an ellipsecan'be obtained by turning the axis 0 0 of the spindle 41 of the toolhead 39 through a certain angle III 0 and displacing the piston rotationaxis 0 0 turned through angle in the horizontal plane (i.e. the planeturning of the tool head spindle) to a value of 1 relative to 0 (curve JFIG. 15).

The piston rotation axis 0 0 is turned through angle A also in thehorizontal plane by means of the carriage 28, angularly turning aroundthe pin 34.

When the piston rotation axis turned through angle A is displaced to adistance of 1 relative to point 0 inthe vertical plane (i.e. the planeperpendicular to the turning plane of the tool head spindle) and at anangle ill a 0 of turning the tool head spindle axis 0 0 we obtainvariable cross sections enveloped by an allipse (curve N, FIG. 15). Inthis case the piston rotation axis 0 0 is turned through angle A in thevertical plane around axis 35 with the aid of gauging blocks.

When the piston rotation axis 0 0 is turned through angle Asimultaneously in two planes, this produces variable asymmetrical curvestwisted in length (not shown in the drawings).

It follows from the above that the machine permits obtaining a range ofoval curves with different degrees of curvature, both symmetrical andasymmetrical, with the same values of the larger and smaller axes andwith a constant cross section along the length of the workpiece.

Besides, the machine makes it possible to obtain variable cross sectionsalong the workpiece machining length, these sections being elliptical,enveloping an ellipse and enveloped by an ellipse, as well asasymmetrical curves.

What is claimed is:

l. A piston-turning lathe comprising: a bed; a moveable table mounted onsaid bed and provided with a head carrying a work spindle; a bridgeinstalled on said bed; a tool head installed on said bridge and providedwith a spindle for cutting tools for the preliminary and finishmachining of pistons during spindle rotation; a longitudinal master formaccommodated inside said tool head spindle and contacting the mechanismfor setting the toolholders with said cutting tools for preliminary andfinish machining; a means for moving said table along said bed; a meansfor synchronous unidirectional rotation of said tool head and work headspindles at twice the angular speed of said tool spindle with relationto said work spindle; means for displacing in two mutually perpendicularplanes the axis of said work head spindle relative to the axis of saidtool head spindle, means for turning the axes of said spindles in thedirection of working feed, means for inclining the axis of said workhead spindle in the same direction; a

means for mutual relative turning of said work head and tool headspindles upon operation of said mechanism for setting the tool holderswith the cutting tools for the preliminary and finish machining of thepistons.

2. A lathe according to claim 1 wherein said means for synchronousunidirectional rotation of said tool head and work head spindles is madein the form of a gear-and-universal-joint drive incorporating a geardrive to the shaft of said tool head with a speed ratio of 1:2 and agear drive to said ,work head spindle with a speed ratio of 1:1, saiddrives being connected with a universal-joint drive.

3. A lathe according to claim 1 wherein said devices for displacing thework head spindle axis relative to the tool head spindle axis in twomutually perpendicular planes are made in the form of screw-and-nutpairs which act in these planes on the body of said work head.

4. A lathe according to claim 1 wherein the axis of said tool headspindle is turned relative to the direction of feed by said bridgeprovided with a pin on which said tool head is installed in such amanner that the axis of said pin passes through the point ofintersection of the axis of said tool head spindle with the planepassing through the tops of said cutting tools of the tool head,perpendicularly to the axis of its spindle.

5. A lathe according to claim 1 wherein means for inclining the axis ofsaid work head spindle in the direction of working feed in the planeperpendicular to the plane of turning of said tool head spindle is adevice in the form of a sine table with inclined plates.

6. A lathe according to claim 1' wherein means for turning the axis ofsaid work head spindle in the direction of working feed in the planecoinciding with or parallel to the plane of turning said tool headspindle is a swivelling carriage with a hole, said hole being slipped onthe pin secured on the upper plate of said sine table.

7. A lathe according to claim 1 whereinthe means for mutual relativeturning of said work head and tool head spindles by said mechanism forsetting the tool holders is made in the form of a vane cylinder whosebody carries a gear of the gear drive of said tool head while the bodyproper is installed with a provision for turning on the drive shaft withwhich the vanes of said cylinder are rigidly "connected.

1. A piston-turning lathe comprising: a bed; a moveable table mounted onsaid bed and provided with a head carrying a work spindle; a bridgeinstalled on said bed; a tool head installed on said bridge and providedwith a spindle for cutting tools for the preliminary and finishmachining of pistons during spindle rotation; a longitudinal master formaccommodated inside said tool head spindle and contacting the mechanismfor setting the tool holders with said cutting tools for preliminary andfinish machining; a means for moving said table along said bed; a meansfor synchronous unidirectional rotation of said tool head and work headspindles at twice the angular speed of said tool spindle with relationto said work spindle; means for displacing in two mutually perpendicularplanes the axis of said work head spindle relative to the axis of saidtool head spindle, means for turning the axes of said spindles in thedirection of working feed, means foR inclining the axis of said workhead spindle in the same direction; a means for mutual relative turningof said work head and tool head spindles upon operation of saidmechanism for setting the tool holders with the cutting tools for thepreliminary and finish machining of the pistons.
 2. A lathe according toclaim 1 wherein said means for synchronous unidirectional rotation ofsaid tool head and work head spindles is made in the form of agear-and-universal-joint drive incorporating a gear drive to the shaftof said tool head with a speed ratio of 1:2 and a gear drive to saidwork head spindle with a speed ratio of 1:1, said drives being connectedwith a universal-joint drive.
 3. A lathe according to claim 1 whereinsaid devices for displacing the work head spindle axis relative to thetool head spindle axis in two mutually perpendicular planes are made inthe form of screw-and-nut pairs which act in these planes on the body ofsaid work head.
 4. A lathe according to claim 1 wherein the axis of saidtool head spindle is turned relative to the direction of feed by saidbridge provided with a pin on which said tool head is installed in sucha manner that the axis of said pin passes through the point ofintersection of the axis of said tool head spindle with the planepassing through the tops of said cutting tools of the tool head,perpendicularly to the axis of its spindle.
 5. A lathe according toclaim 1 wherein means for inclining the axis of said work head spindlein the direction of working feed in the plane perpendicular to the planeof turning of said tool head spindle is a device in the form of a sinetable with inclined plates.
 6. A lathe according to claim 1 whereinmeans for turning the axis of said work head spindle in the direction ofworking feed in the plane coinciding with or parallel to the plane ofturning said tool head spindle is a swivelling carriage with a hole,said hole being slipped on the pin secured on the upper plate of saidsine table.
 7. A lathe according to claim 1 wherein the means for mutualrelative turning of said work head and tool head spindles by saidmechanism for setting the tool holders is made in the form of a vanecylinder whose body carries a gear of the gear drive of said tool headwhile the body proper is installed with a provision for turning on thedrive shaft with which the vanes of said cylinder are rigidly connected.